MÁSTER INTERUNIVERSITARIO EN

ACUICULTURA

Effect of two extruded diets with different

fish and squid meal ratio on growth,

digestibility and body composition of

Octopus vulgaris (Cuvier, 1797).

TRABAJO FIN DE MÁSTER

Alumna: Raquel Monge Ortiz.

Directora Académica: Dra. Ana Tomás Vidal.

Valencia, Septiembre 2012

Contents

1

CONTENTS

Pag.

Abstract / Resumen 2

1. Introduction 4

2. Materials and methods 7

2.1. Animals 7

2.2. Experimental design 7

2.3. Diets 7

2.4. Biochemical analysis 8

2.5. Parameters calculated 9

2.6. Statistical analysis 9

3. Results 10

4. Discussion 13

5. Acknowledgements 16

6. References 17

Abstract

2

Effect of two extruded diets with different fish and squid meal ratio on

growth, digestibility and body composition of Octopus vulgaris (Cuvier,

1797).

Monge R.1

1 Research Group of Aquaculture and Biodiversity. Institute of Animal Science and Technology.

Universitat Politècnica de València. Camino de Vera, 14. 46071-Valencia (Spain).

Abstract

Growth and body composition of Octopus vulgaris fed with two formulated extruded

diets based on different ratio of fish and squid meal (1:1, FMS and 3:1, 3FMS, fish

meal:squid meal) and a natural diet based on crab (Carcinus mediterraneus) and bogue

(Boops boops) were studied in present work. The animals showed a 100% survival rate

in all cases. The best growth results were obtained in control group, where the animals

showed a SGR 2.14±0.18% BW/day, followed by the octopuses fed the FMS diet with

0.59±0.22% BW/day, and finally, the group fed the 3FMS diet, 0.53±0.22% BW/day.

No significant differences were observed between groups FMS and 3FMS. The animals

of control group showed the highest digestive gland index (6.18±0.51), but no

significant differences were shown between the three groups (5.33±0.62 and 5.82±0.62

in FMS and 3FMS respectively). Digestibility was no affected by the type of diet.

Octopuses fed with extruded diets showed an ADC value of 86.9% and 89%, in FMS

and 3FMS respectively. The two extruded diets showed no differences between them

but differ with the Control diet in case of muscle and digestive gland, while present

differences between two extruded diets in case of whole octopus. The results suggest

that both shrimp meal and fish meal could be used for dry pelleted extruded diets, with

good acceptance, but the correct formulation of extruded diets must be studied in order

to obtain a growth similar to the natural one in octopus. The present study reports the

first step in the search for an adequate dry pelleted extruded diet for O. vulgaris.

Keywords: Octopus vulgaris, growth rate, digestibility, extruded diet.

Abstract

3

Resumen

En el presente trabajo se ha estudiado el crecimiento y la composición corporal del

pulpo común (Octopus vulgaris), alimentado con dos dietas extrusionadas con diferente

proporción de harina de pescado y calamar (1:1 y 3:1 de harina de pescado:harina de

calamar), y una dieta natural a base de cangrejo (Carcinus mediterraneus) y boga

(Boops boops). Los animales presentaron una supervivencia del 100% en todos los

tratamientos. Los mejores resultados en el crecimiento se obtuvieron en el grupo

control, en el que los animales mostraron un SGR de 2.14±0.18% BW/día, seguido de

los pulpos alimentados con la dieta FMS, con un crecimiento de 0.59±0.22% BW/día, y

por último, el grupo alimentado con la dieta 3FMS, con 0.53±0.22% BW/día. No se

observaron diferencias significativas entre los grupos FMS y 3FMS. Los animales del

grupo control presentaron el mayor índice de glándula digestiva (6.18±0.51), pero no se

encontraron diferencias significativas entre las tres dietas (5.33±0.62 y 5.82±0.62 en

FMS y 3FMS respectivamente). La digestibilidad no estuvo afectada por el tipo de

dieta. Los pulpos alimentados con las dietas extrusionadas, mostraron un valor de

86.9% y 89%, en FMS y 3FMS respectivamente. Las dos dietas extrusionadas no

mostraron diferencias entre ellas, pero sí respecto a la dieta control, en el caso del

músculo y la glándula digestiva, mientras que si que se encontraron diferencias entre las

dos dietas experimentales y la dieta control en el caso de los pulpos completos. Los

resultados sugieren que la harina de calamar y la harina de pescado pueden ser

utilizadas con los mismos resultados en las dietas secas extrusionadas, con buena

aceptación, pero la correcta formulación de las dietas extrusionadas debe seguir siendo

investigada para poder llegar a obtener crecimientos similares a los obtenidos con las

dietas naturales en el caso del pulpo. El presente estudio representa los primeros pasos

en la búsqueda de una dieta seca extrusionada para O. vulgaris.

Palabras clave: Octopus vulgaris, tasa de crecimiento, digestibilidad, dieta

extrusionada.

Intoduction

4

1. Introduction

The octopus (O. vulgaris) is a benthic, neritic species occurring from the coast line and

living in depths from 0 to 200m (Vaz-Pires et al., 2004). It has a worldwide distribution

in tropical and subtropical waters of the Atlantic, Indian and Pacific oceans, as well as

in the Mediterranean Sea (Mangold, 1983; Quetglas et al., 1998). They are found in a

variety of habitats, such as rocks, coral reefs and grass (FAO, 1984).

Throughout its distribution range, this species is known to undertake limited seasonal

migrations, usually overwintering in deeper waters and occurring in shallower waters

during summer. Their natural diet consist mainly of crustaceans (mostly brachyuran of

the genera Portunus, Dromia, Calappa and Pagurus), shellfish, fish (which includes

species Pagellus, Dentex, Boops and a few soleidae and triglids) and a small percentage

of other cephalopods (Pereiro & Bravo de Laguna, 1979).

Currently only are traded a few species of cephalopods a large scale. The squid (Loligo

vulgaris) is approximately 73% of the catches of cephalopods worldwide, followed by

cuttlefish (Sepia officinalis) with 15% and common octopus (Octopus vulgaris) with 8%

(FAO 2012).

The need to diversify marine aquaculture products that have saturated the market, such

as gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax),

and represent the highest percentage of production in the Spanish market, has stimulated

the development of producing new species (Biandolino et al., 2010).

An ideal candidate for this diversification is the common octopus (O. vulgaris), which is

a species that has drawn great attention to it in recent years (Iglesias et al., 2000;

Navarro & Villanueva, 2000; Vaz-Pires et al., 2004; Almansa et al., 2006; Biandolino

et al., 2010), as it has great potential as an aquaculture product, a great appreciation for

the consumer and an attractive selling price to consider its production (Prato et al.,

2010; Garcia et al., 2011). It has a high nutritional value for human diet because of its

high levels of n3 PUFA (Petza et al., 2011) and a rapid growth rate, about 13% of body

weight per day with natural food (Vaz-Pires et al., 2004). It also adapts quickly and

easily to life in captivity, and has a great resistance to transportation and stress, as well

as a high fertility rate, which makes it a good species for aquaculture (Villanueva,

1995). However, it also presents some problems for industrial production, such as low

larval viability and absence of artificial feeding, which has good nutritional qualities

and is efficient for on growing the species (Vaz-Pires et al., 2004; Domingues et al.,

2007; Quintana et al., 2008; Garcia et al., 2011).

The first works on nutrition with this species took place with natural diets, since the

objective was to adapt it to captivity (Aguado & García García, 2002; García García &

Cerezo Valverde, 2006). But this type of diet also represents a problem. Even though by

Introduction

5

means of it spectacular growth of octopus has been achieved -of the order of a kilo a

month- the increase in the costs of production, the waste excess and the limited

availability of this type of food in the market to ensure the production of the species

make it necessary to search for an artificial diet (MISPECES, 2012).

The first artificial diets tested on octopus (O. vulgaris) were the so-called wet diets

(Cerezo Valverde et al., 2008; Quintana et al., 2008; Estefanell et al., 2011; Garcia et

al., 2011; García-Garrido et al., 2011), which achieved growth from almost zero in the

order of 0.22±0.12% BW/day in Cerezo Valverde et al. (2008), to the one obtained by

García-Garrido et al. (2011), which reached 8.9±5.8% BW/day. Despite the

improvements made in wet diets, they show some disadvantages, just as natural food,

such as the high cost of storage, since they should be kept in cold storage to avoid

spoilage and pathogenic developments due the large quantity of water that these diets

have, and difficulty in manufacture, since it is a process purely made by hand.

Therefore, it is necessary to obtain a dry diet that is accepted by octopuses, and which

grows similarly to natural food. Thus, the use of dry diets presents a great number of

advantages, such as the regular supplies and its composition (MISPECES, 2012), the

fact that it allows us to preserve the quality of the product for a long time, and its easy

transportation and storage, which involve less manipulation, thus reducing infectious

diseases (Mazón et al., 2007). For these reasons, the optimal development of artificial

diets can provide a great improvement in the on growing of the species.

Nevertheless, a dry diet must have a number of special qualities when referring to

octopus. It has to submit specific textural and organoleptic characteristics, which

correspond to their feeding mechanisms and the structure of their digestive system

(Petza et al., 2011).

The first problem in designing an artificial diet for octopus is the acceptance, so that the

animal finds it palatable and eats it completely (Garcia García & Cerezo Valverde,

2006; Cerezo Valverde et al., 2008; Quintana et al., 2008; Querol et al., 2012). The lack

of acceptance is caused, among other reasons, by the diets palatability, since octopuses

have a large number of chemoreceptors in the tentacles, which allows them to

differentiate flavors in a very precise way. Therefore, it seems logical that the diets of

this species contains some sort of flavor enhancer to promote food acceptability (Cerezo

Valverde et al., 2008; Domingues et al., 2007), with the aim of producing more

palatable diets for octopuses.

Another problem to keep in mind in the manufacture of an extruded diet for octopus is

stability. Granulated extruded diets designed for fish are not appropriate in the case of

octopuses, because they disintegrate rapidly before consumption when they are being

manipulated by the animal (Cerezo Valverde et al., 2008). The feed should be stable

Introduction

6

enough so that it does not disintegrate in the water before consumption, or when being

manipulated, since octopuses do not eat the food immediately (Petza et al., 2011). In

several experiments gelatin and alginate were used to improve feed stability in water

and to create a gummy texture that is acceptable to octopuses, both O. vulgaris (Cerezo

Valverde et al., 2008; Garcia et al., 2011), and Octopus maya (Rosas et al., 2008).

For all the mentioned reasons, setting the nutritional requirements for the growth of

common octopus (O. vulgaris) has been complicated (Petza et al., 2011), because the

main objective is to find a form of dry feed that is consumed by this species and with

which a growth similar to that obtained with natural food can be obtained.

A dry feed “base” with a stable structure in water has been recently produced thanks to

gelatin and maltodextrin. It has had a good acceptance by octopus, because it contains a

strong flavoring, like the case of egg yolk (Querol et al., 2012). Parting from this

formula which uses extruded feed, a way to improve the nutritional composition of diets

to enhance growth has been opened.

Due to their natural diet, proteins are the main energy source for the octopus. For this

reason, in this study it had been tested two protein sources, which were, fish meal,

protein source for excellence in the manufacture of feed for aquatic animals, and squid

meal, chosen for its amino acid profile, rich in arginine. Arginine is one of the essential

amino acid for cephalopods, deficient in most commonly used raw materials in the

manufacture of aquatic feeds, including fish meal, so that the squid meal is adequate to

fill this deficiency, thus preventing the need for supplementation with this amino acid.

(Cerezo Valverde et al., 2012).

Therefore, the objective of this study is to evaluate two artificial dry diets made with

fish and squid meal in an on growing experiment, in order to assess its influence on

growth, digestibility and body composition of the octopus.

Material and Methods

7

2. Materials and methods

2.1. Animals

The octopuses (O. vulgaris) were caught using drag nets in Tarragona (Spain) and were

transported to the facilities of IRTA (Institut de Recerca I Tecnologia Agroalimentària).

Before the experiment started, the octopuses were kept in a recirculation seawater

system for ten days. During this period of acclimation, the water temperature was 17-

19ºC, and no mortality was observed. The specimens were fed with crab (Carcinus

mediterraneus).

2.2. Experimental design

During 34 days, eighteen specimens distributed in three groups (six per group) were

placed in individual 250l rectangular fiberglass tanks. Each one containing PVC tubes

as shelters. Two groups were fed with the experimental diets, FMS and 3FMS, and the

control group, fed with crab (C. mediterraneus) and bogue (Boops boops). The

octopuses were fed daily at 9:00h and at 15:00h and, the uneaten food was collected at

14:00 h and at 20:00h, respectively.

Octopuses were weighted individually every 15 days. The octopuses were introduced

individually into a mesh, and weighed, and then were returned to their tank.

The feces of the three groups were used to calculate the digestibility of diets. They were

recollected during the last 10 days of the experiment with a scoop net, water was

removed from them and they were frozen until the analysis.

2.3. Diets

The extruded diets under study had a diameter of 1cm, and 4-5 cm of length, and were

prepared at the Institute of Animal Science and Technology of the Universitat

Politècnica de València, using a semi-industrial extruder; Clextral BC45, under

conditions of 50 ATM and 100 ºC. The difference between diets was the fish- squid

meal ratio, 3FMS diet contained the triple of fish meal than FMS diet (Table 1). A 2%

of Taurine was also added to the composition of the diet in order to promote muscle

growth.

Material and Methods

8

Table 1. Composition of experimental diets (%).

Maltodextrin Gelatin Fish meal Squid meal Yolk Taurine

FMS 9.8 19.6 19.6 19.6 29.4 2

3FMS 9.8 19.6 29.4 9.8 29.4 2

Maltodextrin: PRAL S.A., Gelatin: PILARICA S.A., Fish meal: COCERVA S.C., Yolk: Pasteurised egg

yolk powder (IGRECA SAS), Squid meal: Max Nollert®, Taurine: Sigma-Aldrich logistik.

Extruded diets nutrients are shown in Table 2, around 60% crude protein and 21% crude

lipid in dry matter, respect natural diet. Natural composition was 57% crude protein and

11% crude lipid.

Table 2. Proximate composition (expressed as percentage of wet weight) of

experimental diets.

Control FMS 3FMS

Moisture (%) 78.23 18.61 13.43

Crude protein (%ww) 12.46 49.52 53.38

Crude lipid (%ww) 2.36 16.43 18.56

Ash (%ww) 4.02 15.34 16.04

2.4. Biochemical analysis

At the end of the feeding trial half of the octopuses of each treatment were completely

analyzed, as well as the muscle and digestive gland of the another nine animals, which

were analyzed separately.

The digestive gland was extracted and homogenized, and, the tentacles (muscle) and

complete octopus were filleted, minced into small pieces and mixed until a homogenous

sample was obtained.

Diets, digestive glands, tentacles and whole fish, were analysed according to AOAC

(1990) procedures: dry matter (105 °C to constant weight), ash (incinerated at 550 °C to

Material and Methods

9

constant weight), and crude protein (N×6.25) by the Kjeldahl method after an acid

digestion (Kjeltec 2300 Auto Analyser, Tecator Höganas, Sweden) and crude lipid

extracted with methyl-ether (Soxtec 1043 extraction unit, Tecator).

The apparent digestible coefficient of the two artificial diets was determined by Acid

Insoluble Ash method (Atkinson et al., 1984). The ash was boiled HCl for 5 mins. and

filtered through a low fiber filter (Whatman nº42). Filters were burned in a muffle

furnace at 500ºC during 16h.

2.5. Parameters calculated

The following indices were calculated:

Weight gain: WG =Wf–Wi; Absolute growth rate: AGR= (Wf–Wi)/t; Specific growth

rate: SGR= (LnWf –LnWi); Digestive gland index: DGI= (DGW/Wf)*100; where Wf=

final weight in g; Wi= initial weight in g; t=time in days; DGW= digestive gland

weight.

Apparent digestibility: ACD(%)= 100 - [100*(AIAfeed/AIAfaces)*(nutrient faces/nutrients

feed)], where AIA(%)= (ash of the sample/dry weight of the sample)*100; AIA=Acid

insoluble ash.

2.6. Statistical Analysis

The effect of the different diets on the above indices was analyzed by one-way ANOVA

and the significance of the differences in mean values was analyzed by Neuman-Keuls

test. The statistical assays were carried out with the Statgraphics (Statistical Graphics

System, Version Plus 5.1, Herndon, Virginia, USA) and significance is indicated by P-

values of less than 5%.

Results

10

3. Results

The next figure shows the weight evolution of the octopuses fed the three experimental

diets. Animals which were fed artificial diets had the same behavior, and the growth of

the control group was much higher.

At the end of the experiment the fish survival was not affected by treatment (100%).

Significant differences in fish growth (live weight, AGR and SGR) were observed

(Table 3), as animals fed with Control diet showed significantly better growth indices.

Regarding biometric parameters, digestive gland index (DGI) values were higher in

control (6.18%) than in FMS (5.33%) and 3FMS (5.82%), although these differences

were not significant (Table 3).

Table 3. Mean values±S.D. for growth and biometric parameters of each experimental

group (N = 6).

Values on the same line and different superscripts are significantly different. Wi, initial weight; Wf, final

weight; WG, weight gain; AGR, absolute growth rate; SGR, specific growth rate; DGI, digestive gland

index.

Control FMS 3 FMS

Wi (g) 675.83 ± 82.78 596.25 ± 101.39 735 ± 101.39

Wf (g) 1335 ± 79.31a 720 ± 97.14

b 870 ± 97.14

b

WG (g) 659.17 ± 37.79a 123.75 ± 46.29

b 135 ± 46.29

b

AGR (g/day) 19.97 ± 1.14a 3.75 ± 1.4

b 4.09 ± 1.4

b

SGR (% BW/day) 2.14 ± 0.18a 0.59 ± 0.22

b 0.53 ± 0.22

b

DGI (%) 6.18 ± 0.51 5.33 ± 0.62 5.82 ± 0.62

Figure 1. Evolution of weights.

Results

11

Table 4. Proximate composition (expressed as percentage of wet weight) (N=3) of

muscle, digestive gland and whole octopus.

Initial Control FMS 3FMS

Muscle (Tentacle)

Moisture (%) 81.40 80.17±0.59 81.52±0.59 81.40±0.59

Crude protein (%ww) 15.71 16.56±0.40a 14.76±0.40

b 14.27±0.40

b

Crude lipid (%ww) 0.14 0.47±0.09 0,50±0.09 0,52±0.09

Ash (%ww) 2.20 1.95±0.11 2.22±0.11 1.92±0.11

Digestive gland

Moisture (%) 70.26 61.70±0.60a 57.83±0.60

b 57.50±0.60

b

Crude protein (%ww) 18.74 23.77±0.72a 15.95±0.72

b 16.20±0.72

b

Crude lipid (%ww) 2.09 9.81±1.05a 20.86±1.05

b 19.36±1.05

b

Ash (%ww) 2.20 1.63±0.06 1.40±0.06 1.46±0.06

Whole octopus

Moisture (%) 78.36±0.58a 78.92±0.58

a 82.15±0.58

b

Crude protein (%ww) 17.54±0.40a 15.86±0.40

b 13.80±0.40

c

Crude lipid (%ww) 1.33±0.26 1.70±0.26 0.99±0.26

Ash (%ww) 2.01±0.08 1.93±0.08 1.74±0.08

The main differences in the nutritional composition of octopus fed with the

experimental diets were shown in Table 4. Moisture muscle content in the three diets,

ranged from 80 to 82% with no significance differences. In the case of the digestive

gland moisture, there are no differences between the two extruded diets, but was

significantly lower than control group (61.70% compared with 57.83 and 57.5% in FMS

and 3FMS respectively), and in case of the whole octopus moisture, was significantly

higher in 3FMS diet than in Control and FMS diet.

The crude protein of the muscle, ranged from 14 to 17%; the digestive gland protein,

ranged from 15% to 24%, and whole octopus protein, ranged from 13 to 18%, with

significantly lower values in control group. There were no differences between the two

diets in muscle and digestive gland, but the two experimental diets were significantly

different in whole octopus.

Values on the same line and different superscripts are significantly different. The initial composition of

the whole octopus was not calculated because the octopuses captured were insufficient for performing

this analysis.

Results

12

Regarding lipid content, animals fed Control diet did not show significant differences

with the two artificial diets in the case of muscle and whole octopus, but in the case of

digestive gland, the animals fed with Control diet showed lower values of lipid content

(9.81% compared 20.86 and 19.36% respectively) than the FMS and 3FMS diets.

The percentage of ash in the three groups did not show significant differences between

the different diets, and no differences between muscle, digestive gland and whole

octopus.

Apparent digestibility coefficient (ADC) was no affected by the type of diet (Fig. 2).

Octopuses fed with artificial diets FMS and 3FMS showed a similarly data 86.9% and

89% ADC of dry matter respectively. Control diet ACD was not calculated due to

conservation problems of natural food samples.

Figure 2. ADC (Apparent digestibility coefficient) of

experimental diets.

Discussion

13

4. Discussion

This test took place during only 34 days, due to a sharp increase in the water

temperature of the bay, and because the test was conducted in an open recirculating

system. Within days there was an important drop in intake, so it was decided to end the

feeding test.

Prepared diets presented high levels of protein and similar to natural food (about 60%

protein by dry weight). They also presented total lipid levels of around 21%. This

amount of lipids is greater than that the one present in natural food (10.84%) which

triggered a lower growth of animals fed 3FMS and FMS, since it has been shown that

the lipids interfere with the absorption of proteins, concluding that diets with high

amounts of lipids promote high growth (Domingues et al., 2007) and also the high lipid

diets, producing damage to the nidamental glands (García García & Aguado Giménez,

2002).

Referring to growth, the average weight gain was 123 and 135g, and was obtained for

34 days with specific growth rates (SGR) of 0.59±0.22% BW/day and 0.53±0.22%

BW/day with FMS and 3FMS diets respectively. No significant differences in octopus

growth between the experimental diets, however, both of them were lower than the

Control diet (2.14±0.18% BW/day).

If we compare specific growth rates with other on growing test conducted by O. maya

on growing, we can see either similar results or slightly negative ones with dry diets, as

seen in Domingues et al. (2007) due to a very poor absorption of the dry diet because of

its incorrect formulation, and with moist diets, as in Rosas et al. (2007). A growth

exceeding the one in this study can also be observed in the previous ones, as is the case

of Rosas et al. (2008), with moist diets based on crab paste with a SGR of 1.91±0.14%

BW/day and an initial weight for 350±20g, due to improvements in the agglutination of

diets and the use of gelatin to increase the digestibility. Another example is Águila et al.

(2007), also using moist diets with different concentrations of fishmeal, which obtained

a growth of 0.86% BW/day, both of them have a lower weight to the present study.

In previous fattening studies with O. vulgaris, lower growths than the ones obtained in

this study have been observed. Such is the case of wet diet use by García et al. (2011)

with 0.21±0.28% BW/day. Specific growth rates higher to the ones obtained in this

present study are found in Cerezo Valverde et al. (2008), who obtained a SGR of

0.71±0.22% BW/day. Both of them had a similar weight than present study.

The on growing of O. vulgaris has also been tested (Garcia-Garrido et al. 2011), feeds

were made of fish hydrolyzate mixture and squid in different proportions, which also

tested binding behaviors: alginate and gelatin, obtaining a higher SGR of this study

Discussion

14

(0.89±5.8% BW/day), with a lower weight than the present study, which manifestate a

good performance of squid meal in octopus feed.

There were no significant differences in rates of digestive gland (DGI) which are

positively correlated with animal size, although in the case of the Control diet, this was

slightly higher as seen in previous studies (Cerezo Valverde et al., 2008).

Both feeds have a high digestibility of dry matter, 86.9% and 89% in FMS and 3FMS

respectively. This high digestibility may be due to the use of gelatin in the

manufacturing of diets, since to previous studies have shown that gelatin does not affect

digestibility (Rosas et al., 2007), unlike other binders, such as alginate, this might be

due to the fact that it is a polysaccharide obtained from seaweed, which can not be

digested by the octopus, due to the lack of or low activity of amylases (Águila et al.,

2007).

This digestibility data could not be compared to the control group due to a problem in

the storage of the sample. However, when compared to previous studies with the same

raw materials as the ones fed to the control group, we observe that it was lower, with

96.3% in the case of crab and 94.5% in the case of bogue (Mazón et al., 2007). The

same happened in another test with O. vulgaris where the dry matter digestibility of the

bogue was 98.37% and the crab, 94.6% (Hernandez et al., 2004). In addition, in other

studies with Octopus maya (Rosas et al., 2008) and Enteroctopus megalocyathus (Farias

et al., 2010), we can see that the digestibility of natural feed obtained is these tests was

lower than that obtained in the present work, 82% and 71% respectively, which is even

lower than the digestibility of extruded diets.

Despite the good results, the possible higher digestibility of the Control diet in this trial,

could promote the absorption of nutrients, thus increasing the differences in weight

gains recorded between treatments.

The results of the analysis of the octopus proximal composition showed, in the case of

the study of muscle (tentacles), that statistical differences between artificial diets and

the Control diet appeared only in the case of the protein, and yet the values were very

similar, 14 and 16% respectively. As for total lipid levels, moisture and ash, the values

were similar between treatments and also similar to the results obtained in the initial

octopus analysis.

In a similar study by Cerezo Valverde et al. (2008), no significant differences were

observed between the Control diet and the experimental regarding lipids and proteins as

the results were similar to those obtained in the present study.

However, these differences that are not manifested in muscle composition can be seen

in the digestive gland, in the moisture and the protein and lipids, which doubled the

Discussion

15

levels observed in the control group when compared to extruded feed. The data obtained

is consistent with Cerezo Valverde et al. (2008), which also demonstrated differences in

lipid and protein composition between digestive glands of octopus fed the Control and

experimental diets.

The presence of approximately twice the lipids in the digestive gland of octopuses fed

with the experimental diets compared to those fed the Control diet could be due to the

diets 3FMS and FMS. They have twice the amount of lipids than Control diet, and they

are stored in the gland. Contrary seen in a previous study, as the amount of lipids

present in the gland were much lower than those fed the Control diet (Cerezo Valverde

et al., 2008), this difference may be due that the feed in that study had a three times

lower lipid content than the one used for the present study.

In a comparison between lipid glands with the initial data octopuses, it can be observed

that all vary significantly in moisture, protein and lipid content, both with respect to

artificial diets and with the Control diet. With this we conclude, that the feed for the

octopus during development, is going to affect the composition of the glands notably

more than the muscle ones.

Finally, if we compare the composition of the whole octopus, observing lipid levels and

ash, statistical differences among the three treatments cannot be found, not exceeding in

any of the two parameters the 2% of body composition. However in terms of protein

levels and moisture, and despite the diets being similar, they present statistical

differences, being 3FMS diet the one that has the highest moisture level, and the lowest

value of protein. This difference could be due to a better digestibility of natural food by

octopuses in the control group, consistent with the observations made in previous

studies (Aguado Giménez & García García, 2002; García García & Cerezo Valverde,

2006).

With everything that has been observed, it can be concluded that the use of fish meal

with squid meal can be used in the manufacture of dry diets for octopus, since they were

not rejected by the animal, they did not cause a drastic decline in digestibility, and

octopus muscle composition was not changed (although there was a fattening of the

digestive gland), and growth occurred.

Both artificial diets produced similar growth, as proportions of fishmeal studied

regarding squid meal did not seems to have a determining influence on it.

Acknowledgements

16

5. Acknowledgements

This work was financed by JACUMAR (Secretary of Sea, Ministry of Agriculture,

Food and Environment) and Conselleria d´Agricultura, Pesca, Alimentacio i Aigua

(Generalitat Valenciana).

Thanks to all people of IRTA, especially to Ignasi Gairin, for his collaboration during

the development of this test.

Thanks to Ana Tomás and Pablo Querol for their teachings, their infinite patience and

their help in carrying out this work.

References

17

6. References

AOAC. 2000. Official Methods for Analysis. 17th ed. AOAC International,

Gaithersburg, MD.

Atkinson, J.L., Hilton, J.W. & Slinger, S.J. (1984) Evaluation of acid-insoluble ash as

an indicator of feed digestibility in rainbow trout. (Salmo gairdneri). Canadian

Journal of Fisheries and Aquatic Sciences. 41, 1384-1386.

Almansa, E., Domingues, P., Sykes, A., Tejera, N., Lorenzo, A. & Andrade J.P. (2006)

The effects of feeding with shrimp or fich fry on growth and mantle lipid

composition of juvenile and adult cuttlefish (Sepia officinalis). Aquaculture.

256, 403-413.

Aguila, J., Cuzon, G., Pascual, C., Domingues, P., Gaxiola, G., Sánchez, A.,

Maldonado, T. & Rosas, C. (2007) The effects of fish hydrolysate (CPSP) level

on Octopus maya (Voss & Solis) diet: digestive enzyme activity, blood

metabolites and energy balance. Aquaculture. 273, 641-655.

Aguado, F. & García García, B., (2002) Growth and food intake models in Octopus

vulgaris Cuvier (1797): influence of body weight, temperature, sex and diet.

Aquaculture International. 10, 361-377.

Biandolino, F., Portacci, G. & Prato, E. (2010) Influence of natural diet on growth and

biochemical composition of Octopus vulgaris Cuvier, 1797. Aquaculture

International. 18, 1163-1175.

Cerezo Valverde, J, Hernandez, M.D., Aguado Giménez, F. & García García, B. (2008)

Growth, feed efficiency and condition of common octopus (Octopus vulgaris)

feed on two formulated moist diets. Aquaculture, 275, 266-273.

Cerezo Valverde, J., Martínez-Llorens, S., Tomás Vidal, A., Jover, M., Rodríguez, C.,

Estefanell, J., Gairín, J.I., Domingues, P.M., Rodríguez, C.J., García García, B.

(2012) Amino acids composition and protein quality evaluation of marine

species and meals for feed formulations in cephalopods. Aquaculture

International. in press: doi: 10.1007/s10499-012-9569-6.

Domingues, P.M., López, N., Muñoz, J.A., Maldonado, T., Gaxiola, G. & Rosas, C.

(2007) Effects of a dry pelleted diet on growth and survival of the Yucatan

octopus, Octopus maya. Aquaculture Nutrition, 13, 273-280.

Estefanell, J., Roo, J., Guirao, R., Afonso, J.M. Fernández-Palacios, H., Izquierdo, M.,

Socorro, J. (2011) Efficient utilization of dietary lipids in Octopus vulgaris

(Cuvier 1797) fed fresh and agglutinated moist diets based on aquaculture by-

products and low price trash species. Aquaculture Research, in press,

doi:10.1111/j.1365-2109.2011.03014.x.

FAO, (1984) Species catalogue. Cephalopods of the world. An annotated and illustrated

catalogue of species of interest to fisheries. FAO Fisheries Synopsis. 125 (3)

211-212.

References

18

FAO (2012) Octopus vulgaris. http://www.fao.org/fishery/species/3571/en.

Farias, A., Pereda, S.V., Uriarte, I., Dörner, J., Cuzon, G & Rosas, C. (2010) Evaluating

the effects of formulated moist diets on juveniles of Patagonian octopus

Enteroctopus megalocyathus (Gould 1852). Journal of Shellfish Research. 29(4),

793-798.

García García, B. & Aguado Giménez, F., (2002) Influence of diet on ongrowing and

nutrient utilization in the common octopus (Octopus vulgaris). Aquaculture.

211, 171-182.

García García, B. & Cerezo Valverde, J., (2006) Optimal proportions of crabs and fish

in diets for common octopus (Octopus vulgaris) ongrowing. Aquaculture. 253,

502-511.

García-Garrido, S., Hachero-Cruzado, I., Domingues, P., López, N & Rosas, C. (2011)

Effects of fish hydrolysate (CPSP) on growth and digestive gland lipid

composition of Octopus vulgaris (Cuvier, 1979) juveniles. Aquaculture

nutrition. 17, e825-839.

García, S., Domingues, P., Navarro, J.C¸Hachero, I., Garrido, D. & Rosas, C. (2011)

Growth, partial energy balance, mantle and digestive gland lipid composition od

Octopus vulgaris (Cuvier, 1797) fed with two artificial diets. Aquaculture

nutrition. 17, e174-e187.

Hernández, M.D., García García, B., (2004) Digestibility of natural foods in common

octopus (Octopus vulgaris). Biotechnologies for Quality. Aquaculture Europe,

Barcelona, 412–413.

Iglesias, J., Sánchez, F.J., Otero, J.J & Moxica, C. (2000) Culture of octopus (Octopus

vulgaris Cuvier) Present knowledge, problems and perspectives. CIHEAM -

Cahiers Options Mediterraneennes. 313-312.

Mangold, K.M. (1983) Octopus vulgaris. In: Boyle, P. (Ed.) Cephalopod Life Cicles.

Vol. I, Academic Press, London 335-364.

Mazón, M.J., Piedecausa, M.A., Hernández, M.D. & García García, B., (2007)

Evaluation of environmental nitrogen and phosphorus contributions as a result of

intensive ongrowing of common octopus (Octopus vulgaris). Aquaculture. 266,

226-235.

Mispeces.com (2012) URL: http://www.mispeces.com/noticias/2012/jun/120625-imida-

pienso-pulpo.asp.

Navarro, J.C., Villanueva, R. (2000). Lipid and fatty acid composition of early stages of

cephalopods: an approach to their lipid requirements. Aquaculutre.183, 161-177.

References

19

Pereiro, J.A. & Bravo de Laguna, J. (1979) Dinámica de la Población y Evaluación de

los Recursos del Pulpo del Atlántico Centro-Oriental. Boletín del Instituto

Español de Oceanografía. 40, 69-105.

Petza, D., Katsanevakis, S., Lykouri, N., Spiliotis, V. & Verriopoulos, G. (2011)

Investigation of the potential effect of diet, body mass and maturity on growth

and feed performance of common octopus Octopus vulgaris: an information

theory approach. Aquaculture Nutrition. 17, 348-361.

Prato, E., Portacci, G., Biandolino, F. (2010) Effect of diet on growth performance, feed

efficiency and nutritional composition of Octopus vulgaris. Aquaculture. 309,

203-211.

Querol, P., Morillo-Velarde, P.S., Cerezo Valverde, J., Martinez Llorens, S., Moriño,

A.V, Jover, M., Tomás, A. (2012) First assessment of acceptance of dry

extruded diets for Octopus vulgaris (Cuvier, 1797). Aquaculture research. in

press, doi: 10.1111/are.12006.

Quetglas, A., Alemany, F, Carbonell, A., Merella, P. & Sánchez, P. (1998) Biology and

fichery of Octopus vulgaris Cuvier, 1797, caught by trawlers in Mallorca

(Balearic Sea, Western Mediterranean). Fisheries Research. 36, 237-249.

Quintana, D., Domingues, P. & García, S. (2008) Effects of two artificial diets

agglutinated with gelatin on feed and growth performance of common octopus

(Octopus vulgaris) sub-adults. Aquaculture. 280, 161-164.

Rosas, C., Cuzon, G., Pascual, C., Gaxiola, G., López, N., Maldonado, T. &

Domingues, P. (2007) Energy balance of Octopus maya fed crab and artificial

diet. Marine biology. 152, 371-378.

Rosas, C., Tut, J., Baeza, J., Sánchez, A., Sosa, V., Pascual, C., Arena, L., Domingues,

P. & Cuzon, G. (2008) Effect of type of binder on growth, digestibility, and

energetic balance of Octopus maya. Aquaculture. 275, 291-297.

Vaz-Pires, P., Seixas, P. & Barbosa, A., (2004) Aquaculture potential of the common

octopus (Octopus vulgaris Cuvier, 1797): a review. Aquaculture. 238, 221-238.

Villanueva, R. (1995) Experimental rearing and growth of plantonic Octopus vulgaris

from hatching to settlement. Canadian Journal of Fisheries and Aquatic

Sciences. 52, 2639-2650.